1. Technical Field
The present invention relates to a semiconductor device and a method for fabricating the same.
2. Description of the Related Art
Generally, in order to drive PMOS in a CMOS device, impurity B+ ions implanted inside a poly-silicon forming a gate electrode are moved in a channel direction by applying a bias to the gate electrode.
The moved B+ ions cohere around a boundary of a gate oxide film, negatively influencing a drive of a device. Threshold voltage Vth shift and carrier mobility deterioration are examples of negative influence.
Conventionally, an NO anneal process or a plasma nitrification process progresses after a formation of the gate oxide film to prevent B+ ions from penetrating into the gate oxide film.
However, when a nitride oxide (NO) anneal process progresses, N ions are trapped in the gate oxide film, deteriorating mobility.
Further, when a plasma nitrification process progresses, there is a risk of damage to the gate oxide film by plasma from the process.